linux-ext4 - [PATCH] ext4: Move check under lock scope to close a race.

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Date:	Tue,  7 Apr 2015 21:46:50 -0700
From:	Davide Italiano <dccitaliano@...il.com>
To:	linux-ext4@...r.kernel.org
Cc:	Davide Italiano <dccitaliano@...il.com>
Subject: [PATCH] ext4: Move check under lock scope to close a race.

fallocate() checks that the file is extent-based and returns
EOPNOTSUPP in case is not. Other tasks can convert from and to
indirect and extent so it's safe to check only after grabbing
the inode mutex.

Signed-off-by: Davide Italiano <dccitaliano@...il.com>
---
 fs/ext4/extents.c | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index bed4308..8a9ee08 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4934,13 +4934,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 	if (ret)
 		return ret;
 
-	/*
-	 * currently supporting (pre)allocate mode for extent-based
-	 * files _only_
-	 */
-	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
-		return -EOPNOTSUPP;
-
 	if (mode & FALLOC_FL_COLLAPSE_RANGE)
 		return ext4_collapse_range(inode, offset, len);
 
@@ -4962,6 +4955,15 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 
 	mutex_lock(&inode->i_mutex);
 
+	/*
+	 * currently supporting (pre)allocate mode for extent-based
+	 * files _only_
+	 */
+	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
 	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
 	     offset + len > i_size_read(inode)) {
 		new_size = offset + len;
-- 
2.3.4

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